Chicago’s murder rate is finally falling. Can that keep up?

Homicide rates fall across the country for the past two decades, but in Chicago, that trend has reversed in the past year. In 2012, the city saw 506 homicides, a 16 percent increase over 2011. In January 2013, there were 43 homicides, which, if repeated every other month, would have led to 516 homicides over the course of the year—even more than 2012. But thankfully, that pace didn't keep up. February saw a huge drop, with only 14 homicides reported, the lowest monthly total since 1957.

The Chicago Police Department claims that was achieved through "saturation policing," in which the police department identifies high-crime areas and then focuses districts' energies on them. In February, the CPD identified 10 zones, which account for about 2 percent of Chicago's land area but 10 percent of its violent crimes, and sent 200 officers on overtime patrols in those zones. The approach was a modified version of a policy that Mayor Rahm Emanuel and Commissioner Garry McCarthy had initially abandoned. update: this paragraph originally cited 600 officers on overtime patrol; it's actually 200 every night. We apologize for the error.

Former Mayor Richard Daley and Commissioner Jody Weis used two groups, called the Mobile Strike Force (MSF) and Targeted Response Unit (TRU), that had city-wide jurisdiction and were sent in to saturate neighborhoods experiencing spikes in crime; Emanuel and McCarthy broke up those units and dispersed their cops to districts. Those groups were widely criticized as abusive to the communities they arrived in, even if they were seen as effective. The new groups have specific geographic areas, with the hope being that they'll be more responsive to community interests than their predecessors.

There's suggestive evidence that confiscating illegal guns can reduce crime, but this has not been shown in an experimental setting. (Mel Evans / The Associated Press)

Both "saturation units" and the MSF/TRU approach of Daley can be thought of as a form of what criminologists call "hot spot policing." David Weisburd (George Mason / Hebrew University) and John Eck (University of Cincinnati) define "hot spot policing" as "demand[ing] that the police identify specific places in their jurisdictions where crime is concentrated and then focus resources at those locations." That seems like a pretty good description of what Emanuel and McCarthy are up to.

So does it work? Weisburd and Eck identify five randomized controlled trials of hot-spot policing, all of which found positive effects. The Minnesota Hot Spots Patrol Experiment, conducted from June 1987 to June 1988, found that a hot spots strategy resulted in a 6-13 percent reduction in total crime reports. The Kansas City Crack House Raids Experiment, undertaken from November 1991 to May 1992, found an 8 percent net reduction in crime, though those results decayed as the strategy continued. A study in San Diego found that a kind of hot spots policing in which police raids are followed up with visits to landlords to make sure activity has not started up again results in a 60 percent reduction in crime, relative to having no follow-ups with landlords.

But the most interesting studies they highlight focus on a specific kind of hot spot policing, known as "problem-based" policing, which tailors police methods to particular problems (like drug dealing, or gang violence) and tries to incorporate other government services in the process. This is rather different from what Chicago is up to, and likely superior. Both randomized experiments in this area focused on Jersey City, N.J. One found that hot spot policing combined both with target-specific tactics (videotape surveillance of public spaces, confiscating guns stashed in public areas) and with social service intervention (including aid to the homeless, street trash removal, and better enforcement of liquor and housing codes) resulted in significant crime reduction. More interestingly, the second study compared a normal hot spot intervention to one that incorporated local regulatory agencies and "problem-oriented" tactics, and found the latter to be more effective.

President Obama visits a preschool. Some good preschool programs have been shown to reduce criminality in participants. (AP)

There's good evidence to suggest that non-police resources can play an important role in reducing crime rates. The University of Chicago's Crime Lab evaluated a program called "BAM — Sports Edition," which provides 7th-10th grade boys with small group instruction in social and life skills in school, and sports programming after school. The study, which used a randomized design, found that the program reduced violent crime arrests by 44 percent. There's some evidence that good preschool programs can reduce crime rates overall, but it's mixed. Of the two marquee experiments on the topic, the Perry project found significant reductions in crime by age forty, while the Abecedarian project did not find any effects. Then again, the last follow-ups in Abecedarian were conducted when participants were only 21, so it's possible that a gap opened up later on.

The University of Chicago Crime Lab's Jens Ludwig has found that two other policies could be helpful as well in addition to a Chicago-style hot-spot approach. In a paper coauthored with Duke's Phil Cook, he suggests that "gang-based deterrence," in which gangs are collectively held responsible by police and other government and civil society respondents for violence committed by their members, might be more effective than targeting individual perpetrators. The Kennedy School's Anthony Braga, David Kennedy, Anne Piehl, and Lehman College's Elin Waring found that the Boston Ceasefire program, an intervention in the mid-1990s that used a gang-based approach, was associated with reductions in violence, though their evidence is non-experimental and cannot determine what specific parts of the ceasefire program caused the reductions.

Ludwig and Carnegie Mellon's Jacqueline Cohen have also argued that police patrols designed to confiscated illegal guns being carried in the street can be an effective crime policy. Like gang-based deterrence, highly rigorous experimental evidence doesn't exist on this topic, but their analysis of a Pittsburgh program found that it "may have reduced shots fired by 34 percent and gun shot injuries by as much as 71 percent in the targeted areas."

So Chicago's program uses methods that have a solid research body backing them up, but it could be stronger. It could be more tightly coordinated with social service agencies, more specifically tailored to gang homicide in the way suggested by the "problem-oriented" policing model, and combined with educational and other interventions that have also been shown to have effects.

The problem is that all these cost money. Harold Pollack, co-director of the Crime Lab with Ludwig, suggests that barring a federal program like Community Oriented Policing Services, cities may just not have the resources to do what's necessary. "Many innovative policing strategies are pretty labor-intensive," he says. "In the current budgetary environment, a program such as COPS might be necessary for either hot-spot policing or different community-policing approaches to really take hold." And with the federal government in a budget-cutting mood too, even that may be hoping for too much.